The present invention relates generally to fasteners, and more particularly to U-nut fasteners. U-nut fasteners are used within the automotive and other industries for mounting various components, such as, for example, modules, door panels, hinges, and the like, upon support panels, plates, beams, and the like. U-nut fasteners include a pair of arms coupled together to form a U-shaped spring clip. One conventional U-nut fastener is fabricated by stamping the U-nut from a metallic material. The conventional metallic U-nut fastener includes an internally threaded sleeve or nut member which is integrally formed upon a second one of the arms of the U-shaped spring clip. The internally threaded sleeve is adapted to receive a threaded metallic screw or similar type fastener which is passed through an aperture defined within the support plate or panel.
One drawback associated with conventional stamped metallic U-nut fasteners is that they are typically fabricated using metallic material that is prone to corrosion. To reduce corrosion, conventional metallic U-nut fasteners may be coated with a corrosion resistant material to increase the operational life of the U-nut fastener. However, fabricating U-nut fasteners using a metallic material that may experience corrosion and coating the U-nut fasteners with a corrosion resistant material increases the cost of manufacturing the U-nut fasteners.
Another conventional U-nut is fabricated from a molded plastic material. The plastic U-nut is substantially similar to the metallic U-nut, one difference being that the plastic U-nut includes a non-threaded boss that is adapted to receive a threaded metallic screw. To install the metallic screw into the non-threaded boss, the metallic screw is driven into the plastic boss to form the threads within the plastic boss. This method of installing the screw into the plastic U-nut may cause a premature failure of the molded plastic U-nut. For example, during use, the stress in the plastic, caused by the metallic screw installation, forces the plastic to relax, an effect known as creep. This creep coupled with the uncontrollable vibration induced into the U-nut, such as when the U-nut is installed on a vehicle, may cause the screw to loosen and become disengaged from the U-nut. To reduce stress in the plastic U-nut caused by creep, it has been suggested to mold the plastic U-nut to include multiple threads such that the metallic screw does not cut its own threads into the plastic U-nut, thus reducing stress on the plastic U-nut which may cause creep. However, it is relatively difficult and time consuming to mold a plastic U-nut that includes multiple threads. More specifically, after the molding process is completed, additional time and tools are required to remove the molding material formed within the multiple threads without damaging the threads. For example, an additional tool may be required to remove unwanted material within the plastic threads. Additionally, during installation, since the operator may continue to rotate the screw after the screw has reached the end of its design travel. Since the U-nut is fabricated from a plastic material that is softer than the metallic screw, the operator may be unaware that the screw has reached the end of its design travel and continue rotating the screw. This continued rotation may cause the plastic U-nut to fracture or otherwise fail.
A need remains for a U-nut fastener that is economical to manufacture, that includes a prevailing torque or vibration resistance feature, that is able to prevent an over-torque condition from occurring and thus prevent the threaded fastener from being damaged during installation or operation, and that is also fabricated from a material that resists corrosion or a non-metallic material to prevent corrosion.